Fixes for shutdown sequence, including prevention of a race condition

* Throw an exception if any events, runnables or messages are posted after shutdown. These were previosuly being silently ignored. We really should know about them.
* Don't exit the connection manager thread until the object manager thread exits. This fixes a race condition where the wakeup time of the conmgr thread would determine if it shutdown before or after the object manager, meaning it would sometimes ignore messages around shutdown time.
* Add a shutdown constraint to make the client manager shutdown before the invoker/event/conmgr threads. This gives a single point in the shutdown sequence that applications can use as a constraint (TODO: shutdown groups?)
* Emit a log message for each shutdown method call. This could be very useful in production.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5491 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/server/PresentsServer.java

@@ -158,6 +158,17 @@ public class PresentsServer
 
         // initialize the time base services
         TimeBaseProvider.init(_invmgr, _omgr);
+        
+        // Make the client manager shut down before the invoker and dobj threads. This will help
+        // application code to avoid long chains of shutdown constraints (e.g. msoy bureau manager).
+        // TODO: is this check needed?
+        if (_invoker instanceof PresentsInvoker) {
+            _shutmgr.addConstraint(
+                _clmgr, ShutdownManager.Constraint.RUNS_BEFORE, (PresentsInvoker)_invoker);
+
+        } else {
+            log.warning("Invoker is not a PresentsInvoker", "invoker", _invoker);
+        }
     }
 
     /**